Hybrid brake booster using charging valve

ABSTRACT

A hydraulic brake booster is disclosed which provides a power assist to the vehicle operator when the operator applies the vehicle&#39;&#39;s brakes. The brake booster includes a first valve which restricts flow of fluid through the vehicle&#39;&#39;s hydraulic system to develop back pressure in the latter, thereby providing a source of fluid pressure which is used to operate the booster. A back-up fluid supply is provided which is stored in a conventional fluid pressure accumulator. A second valve within the booster housing is actuated when a malfunction prevents normal development of fluid pressure in the booster. When this occurs, the second valve is opened to communicate the high pressure fluid stored in the accumulator into the booster to provide the power assist. A charging valve is also provided in the vehicle&#39;&#39;s hydraulic system which is adapted to develop back pressure in the latter to communicate at least a portion of the fluid flowing through the system into the accumulator to charge the latter when the hydraulic system functions normally.

United States Patent 1191 Bach [ HYBRID BRAKE BOOSTER USING CHARGINGVALVE 1451 Aug. 14,1973

Primary Examiner-Martin P. Schwadron Assistant Examiner-4t. M. ZupcicAttorney--Ken C. Decker et a1.

[75] Inventor: Lloyd G. Bach, South Bend, 1nd.

[5 7] ABSiTIRACT [73] Asslgnee: The f Corporation South A hydraulicbrake booster is disclosed which provides Ben In a power assist to thevehicle operator when the opera- Flledl 1972 tor applies the vehiclesbrakes. The brake booster in- [21 1 App]. 225,166 cludes a first valvewhich restricts flow of fluid through the vehicle s hydraulic system todevelop back pressure Related Application Dam in the latter, therebyproviding a source of fluid pres- [63] Continuation-impart of Ser. No.172,803, Aug. 18, sure which is used to operate the booster. A back-up1971' fluid supply is provided which is stored in a conventional fluidpressure accumulator. A second valve [52] 11.8. C1. 60/54.5 P, 91/391 R,60/413 within the booster housing is actuated when a malfunc- F15!) b13/ 10, F036 tion prevents normal development of fluid pressure in [58]Field of Search 60/54.5 P, 54.6 P. the booster. When this occurs, thesecond valve is 60/52 B, 51, 413; 91/391 R; 137/115 opened tocommunicate the high pressure fluid stored in the accumulator into thebooster to provide the [56] References Cited power assist. A chargingvalve is also provided in the UNITED STATES PATENTS vehicles hydraulicsystem which is adapted to develop 3,633,363 1/1972 Larsen 60/54.6 Pback Pressure in the latter mmunicate at least a 3,692,039 9 1972 Ewaldet al. 137 115 Portion the fluid flowing thmugh the System the 3,610,10210/1971 Brown 91 391 accumulator to charge the latter when the hydraulic3,575,192 4/1971 McDuff 137/118 system functions normally. 3,677,0077/1972 Goscenchi 60/54.6 P 5 CH 2 D F. 3,353,451 11/1967 031115611 etal..... (so/54.5 P mwmg 3,638,528 2/1970 Lewis 60/51 58 99 42 I04 I02 Z056 5 105' 98 8o 74\ 1 92 H8 84 lo i\ \r e 92 r 62 60 5 v 6:; I 14/0 )7/22 Patented Aug. 14, 1973 2 Sheets-Sheet l Patented Aug. 14, 1973 2Sheets-Sheet 3 NQ mm HYBRID BRAKE BOOSTER USING CHARGING VALVEBACKGROUND OF THE INVENTION This application is a continuation-in-partof copending U.S. Pat. application Ser. No. 172,803, filed Aug. 18,1971, owned by the assignee of the present invention and incorporatedherein by reference.

Because of their smaller size, their lower weight and their ability toproduce a higher output force, hydraulic brake boosters are expected tobe used in lieu of existing vacuum boosters in the near future forproviding a power assist to a vehicle operator when the brakes of thevehicle are applied. However, existing vacuum boosters of the so-calledvacuum-suspended type provide a power assist for a limited number ofstops even after the vehicles engine dies. On the other hand, hydraulicbrake boosters immediately revert to manual operation if a malfunctionshould cause the vehicles engine to die thereby terminating operation ofthe power steering pump, or if the valve used within the booster tocommunicate fluid into the latter should malfunction. Therefore, it isdesirable to provide an auxiliary fluid supply to actuate the brakebooster during the aforementioned conditions when pressurized fluidcannot be communicated into the latter from the vehicles normalhydraulic system. Such an auxiliary fluid supply arrangement isdescribed in the aboveidentified patent application. However, onedeficiency with most such auxiliary fluid supply systems is that theaccumulator is randomly charged when normal back pressure is developedin the hydraulic system by operation of the brake booster or byoperation of the vehicles power steering gear. Since it is possible forthe accumulator to become completely discharged if the brake booster orpower steering gear is not operated, it is desirable to assure that theaccumulator is always fully charged.

SUMMARY OF THE INVENTION Therefore, an important object of my inventionis to provide an auxiliary fluid supply for a hydraulic brake booster inwhich the fluid charge in the latter is maintained at the proper levelat all times while the hydraulic system functions normally.

Another important object of my invention is to provide a hydraulic brakebooster of the open center or flow-through type in which a chargingvalve is also provided in the hydraulic system to charge a pressureaccumulator.

Still another important object of my invention is to permit fluid fromthe vehicle's primary hydraulic system to immediately be communicatedinto the booster pressure chamber should the primary hydraulic systemresume normal operation after a brake application is initiated using thepressurized fluid stored in the accumulator.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of avehicle hydraulic system made pursuant to the teachings of my presentinvention; and

FIG. 2 is a cross-sectional view of a hydraulic brake booster used inthe system illustrated in FIG. ll.

DETAILED DESCRIPTION Referring now to the drawings, the hydraulic brakebooster generally indicated by the numeral 10 is actuated by aconventional brake pedal 12 mounted in the vehicle operators compartmentand is adapted to actuate a conventional automotive master cylinder 114for actuating conventional disc brakes 16 on the front wheels of thevehicle and drum brakes 18 on the rear wheels of the vehicle. Thebooster 10 includes an inlet port 20 which is communicated to the outletor high pressure side of the vehicle's power steering pump 22, and anoutlet port 24 which is communicated with the inlet of the vehiclespower steering gear 26. Booster 10 also includes a return or exhaustport 28 which is communicated to a reservoir (not shown) at the inlet ofthe pump 22, as is the outlet of the power steering gear 26. Thevehicle's hydraulic system further includes a charging valve generallyindicated by the numeral 30 which is preferably made according to theteachings of copending U.S. Pat. application Ser. No. 99,796, filed Dec.21, 1970, owned by the assignee of the present invention andincorporated herein by reference. The charging valve 30 includes aninlet port 32 connected to the high pressure side of the pump 22 andfirst outlet port 34 connected to the inlet port 20 of the booster l0.Charging valve 30 is adapted to restrict flow between the ports 32 and34 so that a predetermined minimum amount of flow is always communicatedto the inlet port 20; however, since flow is restricted, back pressureis developed in the hydraulic system which is communicated through asecond outlet port 36 to an accumulator 38 of a type well known to thoseskilled in the art. The charging valve 30 further has a return orexhaust port 40 which is connected to the reservoir (not shown) at theinlet of pump 22. The outlet of the accumulator 38 is connected to stillanother port 42 on the booster 10.

Referring now to FIG. 2, the booster 10 includes a housing 44 defining abore 46 and a pressure chamber 48 therewithin. A boost piston 50 isslidably mounted within the housing 44 and one end of the latter isexposed to the fluid pressure level in the pressure chamber 48. Anactuating rod 52 connects the piston 50 with the master cylinder 14 foractuating the latter in the conventional manner. A return spring 54yieldably urges the piston 50 to the right viewing FIG. 2, toward thebrake release position. A spool valve generally indicated by the numeral56 is slidably mounted in the bore 46 and is provided with grooves 58and 60 and lands 62, 64, which cooperate with corresponding grooves 66,68 and lands '70, 72 on the wall of the bore 46. As illustrated in thedrawings, the inlet port 20 communicates with the groove 60, the outletport 24 communicates with the groove 64 and the return port 28communicates with the groove 58. A spring 74 yieldably urges an abutment76 carried on the left hand end of the spool valve 56 into engagementwith a shoulder 77 provided on the wall of the bore 14, thereby definingthe brake release position of the spool valve 56. Passage meansgenerally indicated by the numeral 78 communicate the groove 68 with afirst set of ports 80 and a second port 82, both of which nonnallycommunicate the passage means 78, and therefore the groove 68 with thepressure chamber 48.

A secondary valve member includes a sleeve 84 slidably mounted on theright hand end of the spool valve 56, which is movable into a positionclosing communication through the port means 8%, but which is yieldablyurged away from the port means 40 by a spring as.

The spring 86 also retains an annular member 88 for movement with thesleeve 84, the purpose of which will be explained in detail hereinafter.A check valve generally indicated by the numeral 90 preventscommunication from the chamber 48 into the passage means 78 through theport 82, but permits communication in the reverse direction. The checkvalve 90 includes a sphere 92 which cooperates with a valve seat 94. Aporous retainer 96 is also urged against the seat 94 by a spring 98 sothat only a minimum pressure differential is required to urge the sphere92 away from the seat 94.

The port 42 communicates with a second bore 98 within the housing 44. Anannular first valve member 100 is slidably mounted in the bore 98, and asecond valve member 102 is slidably carried within the bore 98. A spring104 yieldably urges the valve member 102 into sealing engagement withthe valve member 100 and thereafter urges the valve members 100 and 102as a unit toward the right viewing FIG. 2, so that the valve member 100is urged into engagement with a shoulder 105 provided on the housing 44.The right hand end of the valve member 102 extends through the openingin the annular valve member 100, so that the valve member 102 may beengaged by the retainer 88.

The brake booster is actuated by actuating means generally indicated bythe numeral 106, which includes an actuating rod 108 slidably mountedwithin the booster housing, one end of which is connected to the brakepedal 12 and the other end of which is slidably received in a blind bore110 defined within the piston 50. A first pivot 112 connects one end oflever means 114 to a bracket 116 carried by the piston 50, and a secondpivot 118 connects the opposite end of the lever means 114 to the sleeve84. A third pivot 120 connects a bracket 122 slidably mounted on the rod108 to the lever means 114 at a point intermediate of the ends thereof.A spring 124 yieldably urges the member 122 into engagement with anabutment 126 provided on the rod 108.

MODE OF OPERATION The various components of the brake booster 10 areillustrated in FIG. 2 in the positions which they assume when the brakesof the vehicle are released. In this position, communication between thegrooves 60 and 68 is prevented, and substantially uninhibitedcommunication is permitted between the grooves 60 and 64 so thatsubstantially all of the fluid flow into the inlet port is immediatelycommunicated to the outlet port 24. The groove 68 is communicated withthe groove 58, so that the pressure chamber 48 is vented to thereservoir at the low pressure side of the pump 22 through the port means80, the passage means 78, the grooves 68 and 58, and the exhaust port28. Since substantially uninhibited fluid communication is permittedthrough the booster 10, no back pressure is developed in the systemexcept by the charging valve unless the power steering gear 26 isoperated. The charging valve 30, as described hereinabove, is adapted todevelop pressure in the hydraulic system even if neither the booster 10nor the power steering gear 26 is operated. The back pressure developedby the charging valve 30 is used to charge the accumulator 38 when thevehicle is first started to thereby provide an immediate auxiliary fluidreserve.

When a brake application is effected, actuation of the brake pedal 12urges the rod 108 to the left viewing FIG. 2, thereby pivoting thelevers 114 about the pivot 112, since the spring 124 is sufficientlystrong to normally maintain the bracket 122' into engagement with theabutment means 126. Therefore, pivoting of the lever means 114 urges thespool valve 56 to the left viewing FIG. 1, since the spring 86 issufficiently strong so that relative movement between the sleeve 84 andthe spool valve 56 is normally prevented. When the spool valve 56 isshifted, the orifice defined between the lands 64 and is reduced,thereby restricting flow between the inlet port 20 and the outlet port24 to develop fluid pressure in the groove 60. At the same time, land 62laps with land 72 to prevent fluid communication between the grooves 68and 58, thereby terminating fluid communication from the pressurechamber 48 to the exhaust port 28. Simultaneously, communication isinitiated between the grooves 60 and 58, so that the high pressure fluiddeveloped in the groove 60 is communicated into the pressure chamber 48through the groove 68, the passage means 78, and the port means and 82.High pressure fluid in the pressure chamber 48 acts upon the right endof the piston 50 to urge the latter to the left viewing FIG. 2, therebyeffecting a brake actuation. Even if the pressure level in the pressurechamber 48 reaches a relatively high level, the valve member 102 remainssealingly engaged with the valve member 100, since the fluid pressure inthe pressure chamber 48 also acts on the end of the valve member 1100 tourge the latter to the left viewing FIG. 2 and maintaining the lattersealingly engaged with the valve member 102.

As is well known to those skilled in the art, a malfunction may preventnormal fluid communication into the pressure chamber 48. For example, ifthe vehicle engine dies, or if the pump 22 fails, or if the pump drivebelt breaks, no fluid pressure can be circulated through the hydraulicsystem. Similarly, if the spool valve 56 sticks, so that it cannot bemoved, fluid pressure cannot be communicated into the pressure chamber48. If such a failure occurs, the operator-applied force collapses thespring 86, moving the retainer 88 into engagement with the end of valvemember 102. Further movement of the sleeve 84 relative to the spoolvalve 56 urges the valve member 102 out of sealing engagement with thevalve member 100, to permit high pressure fluid from the accumulator 38to flow into the pressure chamber 48, where it acts on the right handend of the piston 50 to effect a brake application in the normal manner.It will be noted that as the sleeve 84 moves relative to spool valve 56,the sleeve 84 covers the outlet port means 80, so that fluidcommunication between the pressure clfiljrnber 48 and the passage means78 is prevented. This pi events the high pressure fluid in theaccumulator communicated into the pressure chamber 48 from being leakedfrom the pressure chamber, thus preserving the integrity of the system.While the check valve prevents communication from the pressure chamber48 into the passage means 78, flow from the passage means 78 into thepressure chamber 48 is permitted. Therefore, if the vehicles engineshould be restarted, thus resuming normal operation of the powersteering pump, or if a stuck spool valve should free itself to permitnormal fluid communication into the pressure chamber 48, the highpressure fluid communicated into the passage means 78 is communicatedinto the pressure chamber 48 through the port 82, even if the operatordoes not release the brake pedal, thereby resuming normal operation ofthe booster. It should be noted that, during a stop where the fluidcontent of the accumulator 38 is used to operate the booster 10, highpressure fluid in chamber 48 acts on the right hand end of the spoolvalve 56 while fluid pressure is prevented from communicating to theright hand end of the spool valve 56. Therefore, a hydraulic force isdeveloped urging the spool valve 56 to the left, thereby tending to freea stuck spool.

After a sufficient number of brake applications are effected after amalfunction in the main hydraulic system, the accumulator, of course,will become depleted. When this occurs, the brakes may still be actuatedmanually, since operation of the pedal 12 in this instance will collapsethe spring 124, thereby permitting the end of the rod 108 to engage theend of the blind bore 110, to provide a direct mechanical link betweenthe pedal 12 and the master cylinder 14.

I claim:

1. In a vehicle hydraulic system:

a pump for providing fluid pressure in said system;

a brake booster having an inlet port communicated with the outlet ofsaid pump, an outlet port, a pressure chamber, and first valve meanscontrolling communication between said inlet and outlet ports and saidpressure chamber to effect a brake application;

an accumulator communicated to said brake booster;

and

a charging valve communicated with said pump and with said accumulator,said charging valve permitting flow from said pump through saidhydraulic system while diverting a portion of the flow through saidsystem to said accumulator for maintaining a predetermined minimumpressure level in the latter;

said brake booster including second valve means permitting fluidcommunication from said accumulator into said pressure chamber when abrake application is effected and a malfunction prevents fluidcommunication into said pressure chamber from said inlet port;

said first valve means being shiftable from a first position permittingsubstantially uninhibited communication between said inlet and outletports and preventing communication between said inlet port and saidchamber to a second position restricting flow between the inlet andoutlet ports to develop back pressure in said inlet port andcommunicating said inlet port with said pressure chamber to effect abrake application;

passage means defined within said valve means to communicate said inletport to said pressure chamber when said first valve means is shiftedfrom said first position; and

actuating means slidably carried on said first valve means, saidactuating means moving relative to said first valve means when thelatter is disposed in said second postion to first terminatecommunication from said pressure chamber into said passage means and tothereafter actuate said second valve means to communicate saidaccumulator with said pressure chamber.

2. The invention of claim 1:

said passage means terminating in first and second port meanscommunicating said passage means with said pressure chamber, saidactuating means closing said first port means upon movement of saidactuating means relative to the first valve means; and

check valve means preventing communication through said second portmeans from said pressure chamber into said passage means, but permittingcommunication in the reverse direction.

3. The invention of claim 2:

said check valve means including a valve seating area circumscribingsaid passage means, a retainer, resilient means urging said retainertoward said valve seating area, and a sphere disposed between saidretainer and said seating area.

4. In a vehicle hydraulic system:

a pump for providing fluid pressure in said system;

a brake booster having an inlet port communicated with the outlet ofsaid pump, an outlet port, a pressure chamber, and first valve meanscontrolling communication between said inlet and outlet ports and saidpressure chamber to effect a brake application;

an accumulator communicated to said brake booster;

means for charging said accumulator with the fluid pressure output ofsaid pump;

second valve means permitting fluid communication from said accumulatorinto said pressure chamber when a brake application is effected and amalfunction prevents fluid communication into said pressure chamber fromsaid inlet port;

said first valve means being shiftable from a first position permittingsubstantially uninhibited communication between said inlet and outletports and preventing communication between said inlet port and saidchamber to a second position restricting flow between the inlet andoutlet ports to develop back pressure in said inlet port andcommunicating said inlet port with said pressure chamber to effect abrake application;

passage means defined within said valve means to communicate said inletport to said pressure chamber when said first valve means is shiftedfrom said first position;

actuating means slidably carried on said first valve means, saidactuating means moving relative to said first valve means when thelatter is disposed in said second position to first terminatecommunication from said pressure chamber into said passage means and tothereafter actuate said second valve means to communicate saidaccumulator with said pressure chamber;

said passage means terminating in first and second port meanscommunicating said passage means with said pressure chamber, saidactuating means closing said first port means upon movement of saidactuating means relative to the first valve means; and

check valve means preventing communication through said second portmeans from said pressure chamber into said passage means, but permittingcommunication in the reverse direction.

5. The invention of claim 4:

said check valve means including a valve seating area circumscribingsaid passage means, a retainer, resilient means urging said retainertoward said valve seating area, and a sphere disposed between saidretainer and said seating area.

1. In a vehicle hydraulic system: a pump for providing fluid pressure insaid system; a brake booster having an inlet port communicated with theoutlet of said pump, an outlet port, a pressure chamber, and first valvemeans controlling communication between said inlet and outlet ports andsaid pressure chamber to effect a brake application; an accumulatorcommunicated to said brake booster; and a charging valve communicatedwith said pump and with said accumulator, said charging valve permittingflow from said pump through said hydraulic system while diverting aportion of the flow through said system to said accumulator formaintaining a predetermined minimum pressure level in the latter; saidbrake booster including second valve means permitting fluidcommunication from said accumulator into said pressure chamber when abrake application is effected and a malfunction prevents fluidcommunication into said pressure chamber from said inlet port; saidfirst valve means being shiftable from a first position permittingsubstantially uninhibited communication between said inlet and outletports and preventing communication between said inlet port and saidchamber to a second position restricting flow between the inlet andoutlet ports to develop back pressure in said inlet port andcommunicating said inlet port with said pressure chamber to effect abrake application; passage means defined within said valve means tocommunicate said inlet port to said pressure chamber when said firstvalve means is shifted from said first position; and actuating meansslidably carried on said first valve means, said actuating means movingrelative to said first valve means when the latter is disposed in saidsecond postion to first terminate communication from said pressurechamber into said passage means and to thereafter actuate said secondvalve means to communicate said accumulator with said pressure chamber.2. The invention of claim 1: said passage means terminating in first andsecond port means communicating said passage means with said pressurechamber, said actuating means closing said first port means uponmovement of said actuating means relative to the first valve means; andcheck valve means preventing communication through said second portmeans from said pressure chamber into said passage means, but permittingcommunication in the reverse direction.
 3. The invention of claim 2:said check valve means including a valve seating area circumscribingsaid passage means, a retainer, resilient means urging said retainertoward said valve seating area, and a sphere disposed between saidretainer and said seating area.
 4. In a vehicle hydraulic system: a pumpfor providing fluid pressure in said system; a brake booster having aninlet port communicated with the outlet of said pump, an outlet port, apressure chamber, and first valve means controlling communicationbetween said inlet and outlet ports and said pressure chamber to effecta brake application; an accumulator communicated to said brake booster;means for charging said accumulator with the fluid pressure output ofsaid pump; second valve means permitting fluid communication from saidaccumulator into said pressure chamber when a brake application iseffected and a malfunction prevents fluid communication into saidpressure chamber from said inlet port; said first valve means beingshiftable from a first position permitting substantially uninhibitedcommunication between said inlet and outlet ports and preventingcommunication between said inlet port and said chamber to a secondposition restricting flow between the inlet and outlet ports to developback prEssure in said inlet port and communicating said inlet port withsaid pressure chamber to effect a brake application; passage meansdefined within said valve means to communicate said inlet port to saidpressure chamber when said first valve means is shifted from said firstposition; actuating means slidably carried on said first valve means,said actuating means moving relative to said first valve means when thelatter is disposed in said second position to first terminatecommunication from said pressure chamber into said passage means and tothereafter actuate said second valve means to communicate saidaccumulator with said pressure chamber; said passage means terminatingin first and second port means communicating said passage means withsaid pressure chamber, said actuating means closing said first portmeans upon movement of said actuating means relative to the first valvemeans; and check valve means preventing communication through saidsecond port means from said pressure chamber into said passage means,but permitting communication in the reverse direction.
 5. The inventionof claim 4: said check valve means including a valve seating areacircumscribing said passage means, a retainer, resilient means urgingsaid retainer toward said valve seating area, and a sphere disposedbetween said retainer and said seating area.